android中开启事务的方法正确的是,Android SQLite事务

介绍一个ORM框架，LitePal。

GitHub：https://github.com/LitePalFramework/LitePal

使用方法很简单，导入xx包就不说了。

创建一个类，继承DataSupport。

public class StudentBean extends DataSupport {

private int studentID;

private String studentName;

private String studentAge;

private String studentSex;

private String studentPhone;

public int getStudentID() {

return studentID;

}

public void setStudentID(int studentID) {

this.studentID = studentID;

}

public String getStudentName() {

return studentName;

}

public void setStudentName(String studentName) {

this.studentName = studentName;

}

public String getStudentAge() {

return studentAge;

}

public void setStudentAge(String studentAge) {

this.studentAge = studentAge;

}

public String getStudentSex() {

return studentSex;

}

public void setStudentSex(String studentSex) {

this.studentSex = studentSex;

}

public String getStudentPhone() {

return studentPhone;

}

public void setStudentPhone(String studentPhone) {

this.studentPhone = studentPhone;

}

}

assets目录下创建一个名为litepal.xml的配置文件

application继承LitePalApplication

public class UniversalAndroidApplication extends LitePalApplication {

@Override

public void onCreate() {

super.onCreate();

// 初始化sqlite库

LitePalApplication.initialize(this);

}

}

如何使用？

private void insertWithTs() {

StudentBean studentBean = null;

for (int i = 0; i < 1000; i++) {

studentBean = new StudentBean();

studentBean.setStudentName("小明" + i);

studentBean.setStudentAge("" + i);

studentBean.save();

}

}

private void insertWithoutTs() {

List studentBeanList = new ArrayList<>();

StudentBean studentBean = null;

for (int i = 0; i < 1000; i++) {

studentBean = new StudentBean();

studentBean.setStudentName("小明" + i);

studentBean.setStudentAge("" + i);

studentBeanList.add(studentBean);

}

DataSupport.saveAll(studentBeanList);

}

问题来了，上面两个方法同样是插入1000条数据，区别是什么呢？insertWithTs()调用的是对象的save()，执行1000次；而insertWithoutTs()是把1000个对象放在一个集合中，最后调用一次saveAll()。

看一下两种方法效率如何。

insertWithTs()，单位是毫秒

E/SQLITE: begin --> 1470285148375

E/SQLITE: end --> 1470285156347

E/SQLITE: gap --> 7972

insertWithoutTs()，单位是毫秒

E/SQLITE: begin --> 1470285043075

E/SQLITE: end --> 1470285045001

E/SQLITE: gap --> 1926

差别如此之大，原因在哪里？看源码

save()方法是这样的

public synchronized void saveThrows() {

SQLiteDatabase db = Connector.getDatabase();

db.beginTransaction();

try {

// some code

db.setTransactionSuccessful();

} catch (Exception e) {

throw new DataSupportException(e.getMessage());

} finally {

db.endTransaction();

}

}

而saveAll()呢？

public static synchronized void saveAll(Collection collection) {

SQLiteDatabase db = Connector.getDatabase();

db.beginTransaction();

try {

//code to save collection

db.setTransactionSuccessful();

} catch (Exception e) {

throw new DataSupportException(e.getMessage());

} finally {

db.endTransaction();

}

}

每一次save()都涉及到一个事务的begin和end，当数据量变大时，代码执行效率就会明显低于saveAll()的方式。另外需要注意的是，数据插入属于耗时操作，应开启线程。